MDEV-23187: Assorted assertion failures in json_find_path with certain

collations

Fix by Alexey Botchkov

The 'value_len' is calculated wrong for the multibyte charsets. In the
read_strn() function we get the length of the string with the final ' " '
character. So have to subtract it's length from the value_len. And the
length of '1' isn't correct for the ucs2 charset (must be 2).

include/json_lib.h

@@ -35,6 +35,7 @@ typedef struct st_json_string_t
   const uchar *c_str;    /* Current position in JSON string */
   const uchar *str_end;  /* The end on the string. */
   my_wc_t c_next;        /* UNICODE of the last read character */
+  int c_next_len;        /* character lenght of the last read character. */
   int error;             /* error code. */
 
   CHARSET_INFO *cs;      /* Character set of the JSON string. */
@@ -48,7 +49,7 @@ void json_string_set_cs(json_string_t *s, CHARSET_INFO *i_cs);
 void json_string_set_str(json_string_t *s,
                          const uchar *str, const uchar *end);
 #define json_next_char(j) \
-  (j)->wc((j)->cs, &(j)->c_next, (j)->c_str, (j)->str_end)
+  ((j)->c_next_len= (j)->wc((j)->cs, &(j)->c_next, (j)->c_str, (j)->str_end))
 #define json_eos(j) ((j)->c_str >= (j)->str_end)
 /*
   read_string_const_chr() reads the next character of the string constant

mysql-test/main/func_json.result

@@ -1043,9 +1043,6 @@ SELECT JSON_EXTRACT('{"a":null, "b":10, "c":"null"}', '$.a');
 JSON_EXTRACT('{"a":null, "b":10, "c":"null"}', '$.a')
 null
 #
-# End of 10.3 tests
-#
-#
 # Start of 10.4 tests
 #
 #
@@ -1295,6 +1292,11 @@ SELECT JSON_LENGTH('{"a":"b"}','$','$', 'foo');
 ERROR 42000: Incorrect parameter count in the call to native function 'json_length'
 SELECT JSON_LENGTH();
 ERROR 42000: Incorrect parameter count in the call to native function 'JSON_LENGTH'
+# MDEV-23187: Assorted assertion failures in json_find_path with certain collations
+SET COLLATION_CONNECTION= ucs2_unicode_ci;
+SELECT JSON_VALUE('["foo"]', '$**[0]') AS f;
+f
+foo
 #
 # End of 10.4 tests
 #

mysql-test/main/func_json.test

@@ -665,11 +665,6 @@ SELECT 1 + JSON_VALUE('{"nulltest": null}', '$.nulltest');
 SELECT NULL;
 SELECT JSON_EXTRACT('{"a":null, "b":10, "c":"null"}', '$.a');
 
-
---echo #
---echo # End of 10.3 tests
---echo #
-
 --echo #
 --echo # Start of 10.4 tests
 --echo #
@@ -825,6 +820,12 @@ SELECT JSON_LENGTH('{"a":"b"}','$','$', 'foo');
 --error ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT
 SELECT JSON_LENGTH();
 
+--echo # MDEV-23187: Assorted assertion failures in json_find_path with certain collations
+
+
+SET COLLATION_CONNECTION= ucs2_unicode_ci;
+SELECT JSON_VALUE('["foo"]', '$**[0]') AS f;
+
 --echo #
 --echo # End of 10.4 tests
 --echo #

strings/json_lib.c

@@ -401,7 +401,7 @@ static int read_strn(json_engine_t *j)
     return 1;
 
   j->state= j->stack[j->stack_p];
-  j->value_len= (int)(j->s.c_str - j->value) - 1;
+  j->value_len= (int)(j->s.c_str - j->value) - j->s.c_next_len;
   return 0;
 }